Sunday was the summer solstice in the northern hemisphere. As Earth’s axis tilted, the sun reached its highest position in the sky, bathing the upper latitudes in enduring light. Residents of Fairbanks, Alaska experienced a day lasting nearly 22 hours, while denizens of Duluth, Minnesota witnessed a day lasting a more modest 16 hours.

In this, the International Year of Light, it is only fitting to mention the man who literally wrote the book on light: Ibn al-Haytham. A devout Muslim captivated by science, he believed that seeking truth and knowledge about the natural world would bring him closer to God. His quest — one that was both scientific and spiritual — led him to produce his masterpiece: the Book of Optics. Published roughly a thousand years ago, the tome described light more accurately than ever before, and most importantly, did so with meticulously detailed experimental evidence. Pivotally, Ibn al-Haytham outlined his experiments so that anyone could repeat them. His actions may have constituted the birth of the scientific method, itself.